Light energy irradiators find many applications in manufacturing, universities, research facilities, and in the medical field. Irradiator systems are commonly powered by medium pressure mercury vapor lamps which are sometimes referred to in the art as arc lamps, ultraviolet (UV) lamps, cal rods, or UV curing systems. These systems have a wide range of uses and can be used, for example, in the curing of polymers such as photo polymer paints, the curing of inks and coatings, photo activation of adhesives, production of compact discs, and in photo resistant activation. A UV lamp produces high intensity radiation energy in the UV, visible, and infrared spectrums. This high intensity radiation energy may be used to cure inks, coatings, and adhesives that are applied to a variety of substrates, such as paper, plastic film, wood, and metal. The UV lamp or other light source that is used in these processes is typically supported next to a reflecting surface. The reflecting surface is configured in order to provide either a focused or a non-focused reflection of the light. Typically, when the apparatus is used for the curing of materials, the reflector surface will have an elliptical profile to provide a focused optical configuration. Here, the light energy is concentrated into a narrow beam on the curing surface. Typically, elliptical reflectors are used in curing photo reactive fast moving films and webs and printing inks on paper and plastic film that are carried on a conveyor.
The reflecting surface may also be configured to have a semi-circular or parabolic profile. Such a profile provides for a non-focused optical configuration of the reflected light from the light source. Such an optical configuration may be used in applications seeking to cure thicker or slower moving films such as adhesives.
A mechanical shutter is one common feature found in most high-powered light energy irradiators. The purpose of a mechanical shutter is to serve as a light-blocking device to prevent light from the UV lamp from reaching the substance that is being cured. When the shutter is in a closed position, it contains the radiation energy within the lamp housing to prevent energy exposure to the substrate and the material to be cured. In a common production process, the mechanical shutter will typically close when the production machine stops, in order to prevent thermal damage to the substrate. The mechanical shutter will open when the machine starts production, which therefore allows for complete exposure of the UV light to the UV curable material applied to the substrate that is moving under the UV light source.
Generally, two types of mechanical shutters are used in light energy irradiators. The first type is a rotating shutter. A rotating shutter is typically made of one piece of metal, usually aluminum due to its excellent conductivity. In order to close the shutter, the shutter simply rotates in front of the UV lamp to block the light from the substrate and the material to be cured. A rotating shutter is typically water-cooled to prevent thermal damage to the UV lamp system and the material being cured. However, some of the shutters may be air-cooled.
A second type of shutter is commonly referred to as a xe2x80x9cclam shellxe2x80x9d type shutter. This is so because the shutter is configured to open and close much like a clam shell. The shutter is constructed of two halves that are mirror images of one another and are mounted around the UV lamp. Each half of the shutter pivots around a strategically located pivot pin. When the shutter pivots to its closed position, it completely isolates the UV light within its closed cavity. This of course blocks the light from the substrate and the material to be cured. The shutter may also pivot to its open position to allow for UV light to be imparted onto the substrate and the material to be cured. These types of shutters are typically air-cooled.
Reflector sheets which are typically polished aluminum are mounted inside of the mechanical shutter in order to provide for the proper reflection of light energy from the UV lamp. A significant problem with reflector sheets are that the surface deteriorates over time, decreasing the performance of the light energy irradiator system. Additionally, these reflector sheets are difficult to replace. Current shutters make use of one or more rails along either the whole, or partial length of the shutter to retain the reflector sheets thereon. One way of replacing reflector sheets is to slide the entire reflector sheet out from one piece of the mechanical shutter. Such a procedure is problematic in that, aside from being a slow and difficult process, the new elongated reflector sheet when being slid back into the mechanical shutter may become slightly bent or may allow for air to be trapped between the reflector sheet and the mechanical shutter. In operation after having been replaced, heat from the light source will cause a warping of the reflector sheet due to the air being present between the reflector sheet and the mechanical shutter. Such warping will negatively impact the reflective condition of the reflector sheet resulting in decreased performance of the light energy irradiator system.
FIG. 7 shows a prior art shutter 110. Here, the shutter 110 is housed within a lamp housing 106. The reflector liner 20 is attached to a shutter section 102. This attachment is facilitated by way of a retaining clip 100 which attaches the shutter section 102 and the reflector liner 20.
The current state of the art employs UV lamp systems that have replaceable reflector liners 20 that are removed by disassembling a side of the lamp housing 106 and sliding the reflector liner 20 into a top and bottom retaining groove in a shutter 110 which is normally a very snug fit. This snug fit makes it difficult to slide the reflector liner 20 into position. In some instances, sliding friction can be so high as to cause the reflector liner 20 to bend as it is being forced into position. Such bending will negatively impact the reflector liner""s 20 ability to reflect light energy. Additionally, it will also cause air gaps between the reflector liner 20 and the shutter 110 which consequently reduces heat transmission from the reflector liner 20 into the shutter 110. These air gaps can cause the reflector liner 20 to over heat and warp during lamp operation which will subsequently negatively impact the reflective ability of the reflector liner 20, reduce the light output of the UV lamp system, reduce the life of the reflector liner 20, and could possibly cause the UV lamp system to overheat and impact the life of the lamp. On the other hand, if the reflector liner 20 is cut too small and fits too loosely within the grooves in the shutter, the liner 20 will not properly fit against the shutter 110 which may also cause air gaps between the reflector liner 20 and the shutter 110 and hence produce the same negative results as previously stated.
As shown in FIG. 8, the retaining clip 100 may be attached by the use of a screw 104. One or more retaining clips 100 may be employed along the length of the prior art shutter 110 as shown in FIG. 9. Here, three retaining clips 100 are employed on one section of the prior art shutter 110 and four retaining clips 100 are employed along the length of another section of the prior art shutter 110. The retaining clips 100 are mounted every few inches along the length of the prior art shutter 110, and are not continuous along the length of the prior art shutter 110. As shown in FIG. 7, such a configuration does not prevent the occurrence of air gaps between the reflector liner 20 and the shutter section 102 hence resulting in a warped area 98 of the reflector liner 20. Further, the retaining clips 100 do not help conform the reflector liner 20 to the shape of the shutter section 102, but only help to retain the reflector liner 20 onto the shutter section 102. Since the retaining clip 100 does not force the reflector liner 20 to conform to the elliptical shape of the shutter section 102, the potential for air gaps and warpage of the reflector liner 20 is not eliminated.
Although shown as having multiple retaining clips 100, prior devices have been designed having one single, continuous retaining clip 100. Other problems in prior art shutters exist in the fact that the shutter must be completely removed from the lamp housing in order to remove and/or replace the reflector liners.
The present invention improves upon previous light energy irradiators by providing for an improved shutter that allows for a reflector liner to be easily removed and replaced. The present invention also provides for the replacement of the reflector liner in which warping of the reflector liner is not present once operation of the light energy irradiator begins.
Various features and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned from practice of the invention. The present invention provides for a shutter that is used in controlling light from a light source. The shutter includes a first section, that has an engaging member, and that has an inner receiving surface for receiving at least part of a reflector liner. A second section, also with an engaging member, is present and also has an inner receiving surface. The second section is removably securable to the first section. The sections cooperate to provide adequate force to the reflector liner to cause the reflector liner to be retained on the inner receiving surfaces between the engaging projections during attachment of the first and second sections. Detachment of the second section from the first section allows for the removal of the reflector liner from the receiving surfaces.
The shutter of the present invention may be either a rotatable shutter or a clam shell shutter. Further, the shutter may be made of aluminum and may be formed by extrusion. A plurality of fins may be disposed on one or more of the sections in order to dissipate heat that is transferred from the light source.
The present invention also provides for a shutter as described above where one of the first or second sections has a male tapered groove that mates with a female tapered groove located on the other of the first or second sections. This mating occurs when the first and second sections are attached to one another and makes the two sections self-aligning when attached together, for example when bolted to one another. The male and female taper also help insure that the reflector liner is held in position with the correct amount of pressure and that a desired shape of the reflector liner is correctly formed and sustained. In an alternative exemplary embodiment to the present invention, the male and female tapered grooves extend along the entire length of the first and second sections. Such an arrangement helps to insure a mechanical hold between the two sections along the entire length of the shutter to help prevent warping.
A plurality of apertures may be present on the first or second section in order to provide for a pivot point of the mechanical shutter. The apertures may be sized and placed so that the shutter is retrofitable into existing UV lamp systems.
An alternative exemplary embodiment of the present invention exists in a shutter as described above where the reflector liner is attached against the inner receiving surfaces such that the potential for air gaps between the reflector liner and the inner receiving surfaces is eliminated. Such an arrangement may be made in which the first and second sections receive the reflector liners in matingly flush engagement along the entire length of the first and second sections.
A further exemplary embodiment exists in a shutter disposed in a lamp housing that includes a first section and a second section. The first section has a receiving surface onto which a reflector liner may be retained through attachment of the second section to the first section. The reflector liner may be replaced without having to remove the first and second sections from the lamp housing.